1. Field of the Invention
The present invention relates to dynamic pressure bearing devices, each equipped with a dynamic pressure bearing member that supports a rotation shaft with dynamic pressure generated by lubricating fluid.
2. Related Background Art
In recent years, the development of dynamic pressure bearing devices in which rotation shafts are supported by having lubricating fluid generate dynamic pressure has been underway in order to create bearing devices that can rotate rotary bodies at high-speeds and high precision in various types of rotary drive devices. In such dynamic pressure bearing devices, those having a thrust bearing section SB structured as indicated in FIG. 13, for example, have recently been proposed in order to make the entire device thinner. With respect to the thrust bearing section SB indicated in this figure, a rotary member 3 is attached to a rotary shaft 2, which is supported in a freely rotatable manner by a dynamic pressure bearing member 1, and an inner end surface (bottom end surface) in the axial direction at the center part of the rotary member 3 is positioned opposite and in close proximity in the axial direction to an end surface (top end surface) in the axial direction of the dynamic pressure bearing member 1, thereby forming the thrust bearing section SB.
In the interior of the thrust dynamic pressure bearing section SB, an appropriate amount of a lubricating fluid (omitted from drawings) is filled and herringbone-shaped dynamic pressure generating grooves, for example, are formed concavely in a ring shape as a dynamic pressure generating means for the lubricating fluid, so that the pressurizing effect of the dynamic pressure generating grooves causes dynamic pressure to be generated in the lubricating fluid and thereby yields a predetermined levitation force in the axial direction.
In the meantime, a fluid sealing section 4 comprising a capillary sealing section is formed in an area on the outer side in the radial direction of the thrust dynamic pressure bearing section SB, in order to prevent the lubricating fluid within the thrust dynamic pressure bearing section SB from flowing out. The fluid sealing section 4 can be formed by making use of an outer circumference wall surface of the dynamic pressure bearing member 1, for example. More specifically, a tapered sealing space is created by forming an appropriate gap between the outer circumference wall surface of the dynamic pressure bearing member 1 and an inner circumference wall surface of a counter plate 5, which is attached to the rotary member 3 to serve also as a fall-out stopping member, and by gradually enlarging the gap towards an opening section at the bottom.
To fill the lubricating fluid into the thrust dynamic pressure bearing section SB having such a structure, normally a vacuum pumping device is used to fill the lubricating fluid through the fluid sealing section 4. More specifically, the lubricating fluid is allowed to flow downward along the outer circumference wall surface of the dynamic pressure bearing member 1 and into the fluid sealing section 4. After the lubricating fluid is filled, residual lubricating fluid in the form of oil drops and/or films that are adhering to the outer circumference wall surface of the dynamic pressure bearing member 1 is removed by wiping with a solvent to clean the dynamic pressure bearing member 1.
A convex partition step section 6 is formed on the outer circumference wall surface of the dynamic pressure bearing member 1 and near the opening section of the fluid sealing section 4. The convex partition step section 6 projects outward in the radial direction and that partially covers the opening section of the fluid sealing section 4. Due to an effect derived from the shape (i.e., shape effect) of an edge section 6a of the partition step section 6, the lubricating fluid clinging to the outer circumference wall surface of the dynamic pressure bearing member 1 is effectively separated in a lubricating fluid removal process. In other words, the lubricating fluid that clings to the outer circumference wall surface of the dynamic pressure bearing member 1 separates into lubricating fluid in the area on the fluid sealing section 4 side (up in the figure) and lubricating fluid in the area on the opposite side of the fluid sealing section 4 side (down in the figure) with the partition step section 6 as the boundary, which allows the lubricating fluid removal process to be performed smoothly.
However, in the conventional device described above, due to the fact that the convex partition step section 6 has a shape that projects out and substantially cover the opening section of the fluid sealing section 4, the convex partition step section 6 becomes a visual obstacle to visually checking the amount of the lubricating fluid within the thrust dynamic pressure bearing section SB. In other words, the convex partition step section 6 blocks the view of the lubricating fluid that has been filled into the fluid sealing section 4 when the operator tries to see the liquid level of the lubricating fluid that has been filled into the fluid sealing section 4. Although the amount of the lubricating fluid within the thrust dynamic pressure bearing section SB may preferably be as much as possible from the perspective of lengthening the life of the thrust dynamic pressure bearing device, if the amount filled is excessive, the lubricating fluid is more prone to leaking outside through the opening section of the fluid sealing section 4, which can shorten the life of the dynamic pressure bearing device. Especially in devices that require a highly clean environment such as hard disk drive devices (HDDs), leaking of the lubricating fluid can cause contamination of internal equipment and lead to fatal problems for the entire device.
Consequently, a required and sufficient amount of the lubricating fluid must be filled within the thrust dynamic pressure bearing section SB, and to that end the amount of the lubricating fluid filled must be thoroughly checked visually. However, in conventional devices with the convex partition step section 6, visually checking the presence and/or the level of the lubricating fluid filled within the thrust dynamic pressure bearing section SB is difficult, which can diminish the reliability of the dynamic pressure bearing device.
In view of the above, the present invention relates to dynamic pressure bearing devices, as well as methods for manufacturing the same, in which the amount of lubricating fluid filled within thrust dynamic pressure bearing sections SB can be easily checked using simple configurations.
In order to solve the problem described above, a dynamic pressure bearing device in accordance with an embodiment of the present invention includes: a dynamic pressure bearing member and a fluid sealing section adjacent to the dynamic pressure bearing member, the dynamic pressure bearing member defining an outer circumference wall surface whose outer diameter dimension decreases in a direction in which the outer circumference wall surface of the dynamic pressure bearing section becomes removed in the axial direction from the fluid sealing section; and a ridge section provided in a specified area on the outer circumference wall surface of the dynamic pressure bearing member removed in the axial direction from the fluid sealing section, wherein the ridge section defines a surface that discontinuously bends along the axial direction in the outer circumference wall surface of the dynamic pressure bearing member.
In other words, according to the dynamic pressure bearing device having such a configuration, when an opening section of the fluid sealing section is viewed along the outer circumference wall surface of the dynamic pressure bearing member, the entire outer circumference wall surface of the dynamic pressure bearing member including the ridge section recedes towards the center from an axis of line of sight of the opening section of the fluid sealing section. As a result, in a lubricating fluid filling process, for example, the interior of the opening section of the fluid sealing section can be easily seen by a worker. By looking at the liquid level of the lubricating fluid inside the fluid sealing section, the overall amount of the lubricating fluid filled to reach the fluid sealing section, including a thrust dynamic pressure bearing section SB, can readily be checked.
Further, in a process to remove excess lubricating fluid that clings to the outer circumference wall surface of the dynamic pressure bearing member, a shape effect of the ridge section impedes the lubricating fluid from flowing; this effectively prevents residual lubricating fluid from flowing into the fluid sealing section, which allows the lubricating fluid removing process to be performed efficiently and effectively.
In the dynamic pressure bearing device according to the present invention, the ridge section may consist of an edge section of a step section. In addition, in a dynamic pressure bearing device according to the present invention, the ridge section may consist of an edge section of an intersecting section that is defined between an inclined tapered surface extending at an appropriate angle to a center axis line and another surface, which forms a surface that discontinuously bends along the axial direction. By the structures described above, the ridge section can be easily formed through such configurations.
In a method for manufacturing a dynamic pressure bearing device in accordance with an embodiment of the present invention, an outer circumference wall surface of a dynamic pressure bearing member is formed in a shape whose outer diameter dimension decreases in the direction the outer circumference wall surface of the dynamic pressure bearing section becomes removed in the axial direction from a fluid sealing section, and a ridge section is provided in a specified area on the outer circumference wall surface of the dynamic pressure bearing member removed in the axial direction from the fluid sealing section, wherein the ridge section defines a surface that discontinuously bends along the axial direction in the outer circumference wall surface of the dynamic pressure bearing member. As a result, the shape effect of the ridge section prevents the lubricating fluid and a lubricating fluid removing solution from flowing into the fluid sealing section in a lubricating fluid removing process.
In other words, according to the method for manufacturing the dynamic pressure bearing device having such a configuration, when an opening section of the fluid sealing section is viewed along the outer circumference wall surface of the dynamic pressure bearing member, the entire outer circumference wall surface of the dynamic pressure bearing member including the ridge section appears to be receded and pulled in towards the center from an axis of line of sight of the opening section of the fluid sealing section. As a result, in a lubricating fluid filling process, for example, the interior side of the opening section of the fluid sealing section can be easily seen by a worker; and by looking at the liquid level of the lubricating fluid inside the fluid sealing section, the overall amount of the lubricating fluid filled to reach the fluid sealing section, including a thrust dynamic pressure bearing section SB, can be easily checked.
Further, in a process to remove excess lubricating fluid that clings to the outer circumference wall surface of the dynamic pressure bearing member, the shape effect of the ridge section impedes the lubricating fluid from flowing, which effectively prevents residual lubricating fluid from flowing into the fluid sealing section, and which allows the lubricating fluid removing process to be performed efficiently and effectively.
Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, various features of embodiments of the invention.